The All Blacks' midfield stocks have taken a further blow with Conrad Smith sidelined for around six weeks following eye surgery.

Smith will miss the first phase of the Rugby Championship which kicks off with a Bledisloe Cup test against the Wallabies in Sydney on August 18. He will almost certainly miss the rematch in Auckland a week later.

Hurricanes doctor Ian Murphy confirmed Smith's problems today.

"Conrad had two procedures on his left eye for a retinal detachment last week, with the second on Friday. They both went well and he is now recovering at home. At this stage he is expected to be out of training for six weeks," Dr Murphy said in a statement.

Smith's absence comes on the back of the long-term shoulder problem for Chiefs' centre Richard Kahui and the impending departure of second-five Sonny Bill Williams.

The 30-year-old Smith, who has played 58 tests since 2004, has become the first choice No 13 in the All Blacks. He was part of the World Cup winning side and was involved in all three tests against Ireland in June.

The All Blacks selectors are due to name a wider training squad to attend a two-day camp in Wellington next week.